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potentially represents a trough. The water from the edges of this trough flows back obliquely toward the middle, and by the time it reaches the middle it gains such momentum that the middle of the stream is made the highest. Every stream is by these forces resolved into two cylinders, revolving spirally on parallel axes in opposite directions—that is, outward at the bottom, upward at the edges, inward at the top, and downward through the middle. The principle is denominated "the law of the double spiral," and affords an explanation of all the phenomena in question. Since glaciers are subject to the same conditions, it is believed that they are subject to the same movements. It is believed to apply to air currents also, and that the Western blizzard and the Texas norther may be in part due to waves of cold air descending to take the place of that which friction has caused to ascend the Rocky Mountains.

Diffusion of Jade.—Inferences that extensive intercourse between distant regions prevailed in prehistoric times have been drawn from the general dispersion of jade ornaments in the monuments all over the world, and the paucity of known sources of the mineral. Many possible sources of jade have, however, been discovered within a few years, in view of which the necessity of men anywhere having to go to the ends of the earth for their treasure becomes less apparent. Mr. F. W. Rudler recently mentioned to the Anthropological Institute, as among the later discoveries of jade in situ, those of Herr Taube, of Breslau, at Jordans Mühe in Silesia, and at Reiehenstein; the rough pebbles that have been found in the valleys of the Sann and the Mur in Styria; Dr. Dawson's account of the occurrence of bowlders partly sawn through on the Fraser River; and the discovery by Lieutenant Stoney of the mineral in situ at the Jade Mountains, north of the Konak River, in Alaska.

Medicine in Thibet.—The course of instruction at the Thibetan University of the Guinoie Ozero Monastery is very elaborate and is adjusted for ten years of studentship. It includes the Thibetan and Mongolian languages, religion, drawing, handicrafts, astronomy, astrology, philosophy, and theology. The medical course requires three years. The Thibetan medical authorities, according to the Russian M. Ptitsyn, recognize 101 fundamental diseases; and 429 names of elements of drugs used by them are given. Of the 101 diseases, only two (paralysis and a kind of influence of the planets) are attributed to a mythical origin; and of the 429 drugs, only three (the bones of a dragon, the horns and the skin of the unicorn) have a similar derivation. The remainder of the drugs are chiefly herbs, seeds, fruits, roots, and flowers, and partly mineral matters. All, except quinine, which is bought in Russia, are obtained in Chinese drug-shops. M. Ptitsyn visited one of the drug-shops, and found all drugs kept in order in separate drawers. He has brought samples of 202 drugs to St. Petersburg, and they will be analyzed by the Medical Academy.

NOTES.

The fourth season of the Marine Biological Laboratory at Wood's Holl, Mass., Dr. C. 0. Whitman, director, will open for teachers and students, with courses of seven weeks' instruction in zoology, botany, and microscopical technique, July 8th. The first week will be devoted to the study of the lobster, the second to annelids, the third to coelenterates, the fourth to mollusks, the fifth to echinoderms, the sixth to crustaceans, and the seventh to vertebrates (marine). The laboratory for investigators will be open from June 1st to August 20th, furnished with aquaria, glassware, reagents, etc., but not with microscopes and microtomes.

M. de Quatrefages lately reported to the French Academy of Science the discovery, by M. Wanzel, of the skull of a cave bear bearing the marks of a wound that had been received from a stone hatchet. The wound had healed, with the formation of a callus. Two pieces of the hatchet had been broken off by the blow, one of which was left in the wound and had been covered by the callus.

The Pope has written a letter announcing the re-establishment of the donation for the astronomical observatory at the Vatican. He declares that he is solicitous for the progress of science, and places the observatory in the same rank with other papal institutions.

The seventieth birthday of Prof. Helmholtz will occur in August next, and, in anticipation of the event, Profs. Virchow and Du